"Detecting alien 'hair spray' in the atmosphere of an exoplanet would be a strong signal for intelligent life existing on the surface," writes the Blue Marble Space Institute of Science in its plea for private funding on the science-research community website, Petridish.

The reason for the BMSIS's eagerness to search for exoplanetary CFCs is simplicity itself. "There are no known natural process that can create chlorofluorocarbons in the atmosphere," they write, "which makes them a great candidate as 'biosignature'."

Biosignature is bioboffinary lingo for any sign of life – and for astrobioboffins it means anything that can be detected out there in the cosmos that could indicate past or present life on another planet. Such as CFCs.

Specifically, the folks at BMSIS believe that an advanced alien civilization may have used the radiative-forcing powers of greenhouse-gas CFCs to terraform a planet.

For example, let's say we puny humans someday decide that Mars would be a nice place to live, but that it's uncomfortably cold. Well, we could pump shedloads of CFCs into its atmosphere, their greenhouse effect would trap the sun's heat much as carbon dioxide, methane, and nitrous oxide are currently doing here on our own planet, and presto: in no time at all, Gale crater would be as warm as Miami.

Well, maybe it's not quite that simple, but you get our point.

The BMSISers postulate that a planet-hopping alien civilization may have worked just that magic on an otherwise uninhabitable orb, and due to the distinct light-wavelength absorption qualities of CFCs, such terraforming gas should be detectable from our perch here on Earth.

There are certainly enough exoplanets to test for CFCs. As of this Tuesday, the count on Exoplanet.eu sits at 852 planets in 671 planetary systems. Should one of them be found to have CFCs in its atmosphere, there's a decent chance that someone – or something – put it there.